A site selection of potential observatory locations in Turkey have been carried out by using Multi-Criteria Decision Analysis (MCDA) coupled with Geographical Information Systems (GIS) and satellite imagery which in turn reduced cost and time and increased the accuracy of the final outcome. The layers of cloud cover, digital elevation model, artificial lights, precipitable water vapor, aerosol optical thickness and wind speed were studied in the GIS system. In conclusion of MCDA, the most suitable regions were found to be located in a strip crossing from southwest to northeast including also a diverted region in southeast of Turkey. These regions are thus our prime candidate locations for future on-site testing. In addition to this major outcome, this study has also been applied to locations of major observatories sites.Since no goal is set for the best, the results of this study is limited with a list of positions. Therefore, the list has to be further confirmed with on-site tests. A national funding has been awarded to produce a prototype of an on-site test unit (to measure both astronomical and meteorological parameters) which might be used in this list of locations.

New BVR light curves and times of minimum light for the short period β Lyrae system V Tri were analyzed to derive the physical parameters of the system. The light curves were obtained at Ankara University Observatory and at the TÜBİTAK National Observatory during 5 nights in 2001 and 2002. A new ephemeris is determined for the times of primary minimum. The analysis of the light curves is made using the Wilson-Devinney 2003 code. The present solution reveals that V Tri is a near-contact system with a mass ratio near 0.5. The absolute radii and masses estimated for the components, based on our photometric solution, are R1 = 1.94 R , R2 = 1.44 R , M1 = 2.68 M , M2 = 1.36 M , respectively, for the primary and secondary components. The period variation of the system can be attributed to the light-time effect. With the assumption of a coplanar orbit of the third body its revealed mass is m 3 = 0.17 M .

Context. As part of our international program aimed at obtaining accurate physical properties of trans-Neptunian objects (TNOs), we predicted a stellar occultation by the TNO (38628) Huya of the star Gaia DR2 4352760586390566400 (mG = 11.5 mag) on March 18, 2019. After an extensive observational campaign geared at obtaining the astrometric data, we updated the prediction and found it favorable to central Europe. Therefore, we mobilized half a hundred of professional and amateur astronomers in this region and the occultation was finally detected by 21 telescopes located at 18 sites in Europe and Asia. This places the Huya event among the best ever observed stellar occultation by a TNO in terms of the number of chords. Aims. The aim of our work is to determine an accurate size, shape, and geometric albedo for the TNO (38628) Huya by using the observations obtained from a multi-chord stellar occultation. We also aim to provide constraints on the density and other internal properties of this TNO. Methods. The 21 positive detections of the occultation by Huya allowed us to obtain well-separated chords which permitted us to fit an ellipse for the limb of the body at the moment of the occultation (i.e., the instantaneous limb) with kilometric accuracy. Results. The projected semi-major and minor axes of the best ellipse fit obtained using the occultation data are (a′, b′) = (217.6 ± 3.5 km, 194.1 ± 6.1 km) with a position angle for the minor axis of P′ = 55.2° ± 9.1. From this fit, the projected area-equivalent diameter is 411.0 ± 7.3 km. This diameter is compatible with the equivalent diameter for Huya obtained from radiometric techniques (D = 406 ± 16 km). From this instantaneous limb, we obtained the geometric albedo for Huya (pV = 0.079 ± 0.004) and we explored possible three-dimensional shapes and constraints to the mass density for this TNO. We did not detect the satellite of Huya through this occultation, but the presence of rings or debris around Huya was constrained using the occultation data. We also derived an upper limit for a putative Pluto-like global atmosphere of about psurf = 10 nbar.

Radial velocities and proper motions of the Hipparcos Input Catalogue have been used for a preliminary study of the motions of the variable and 'non-variable' carbon stars. Large uncertainties in distances and the fact that a large fraction of the 'constant' stars are suspected variables make separation into variable and constant carbon stars barely significant. On the other hand, the mean motions of the N-and R-type carbon stars are not the same: for the mean galactic velocity components we obtain (w, v, w) = (-15 ± 4, -19 ± 4, -7±8) kms" 1 from 155 N-type stars and (0±13, -43±14,13±17) kms" 1 from 74 R-type stars. The dispersions about the solutions are 31 and 71 kms -1 , respectively. If the 'high velocity' stars with residuals exceeding 3σ are excluded one obtains (-14 ± 3, -15 ± 3, -6 ± 7) kms -1 from the N-type stars, and (-9 ± 8, -16 ± 8, -22 ± 10) from the R-type stars. Of the 8 stars excluded from the solution, 6 stars are of type R. The nature of these 'high velocity' stars is discussed. Solutions including differential galactic rotation and the implied mean absolute magnitude are also discussed. available at https://www.cambridge.org/core/terms. https://doi.

Brightness distribution of variable stars was investigated based on good Hipparcos parallaxes of semiregular variables (SRVs) in the solar neighborhood, and it is shown that the order of the variability types Lb, SR, SRb, SRa, and Mira is, statistically, an order of increasing brightness along the red giant branch and asymptotic giant branch. In addition, it is also shown that the majority of Miras are above and majority of SRVs are below the tip of the red giant branch. The periods of SRVs that fall in Wood's sequence C (fundamental mode) of large Magellanic clouds were identified. Statistically, the order of SR, SRb, and Mira variables with increasing period and increasing absolute magnitude is the same in six infrared (IR) band wavelengths. The slope of the P-L relation for SR + SRb variables in sequence C increases systematically with wavelength in the near IR. This indicates that circumstellar IR emission increases with increasing period from the shorter period SRVs to Miras, which is consistent with the high mass loss rate found in long period Miras. (J-K)-M K diagram suggests that the sequence Lb, SR, SRb, SRab (emission), and Mira may be an evolutionary sequence.